Error unmarshalling knowledgeSession with Facts inserted in entry-points

When trying to marshall and then unmarshall a StatefulKnowledgeSession where a Fact has been inserted into an entry-point a NullPointerException is thrown:

java.lang.NullPointerException
at org.drools.reteoo.RuleTerminalNodeLeftTuple.<init>(RuleTerminalNodeLeftTuple.java:151)
at org.drools.reteoo.RuleTerminalNode.createLeftTuple(RuleTerminalNode.java:608)
at org.drools.marshalling.impl.InputMarshaller.readLeftTuple(InputMarshaller.java:523)
at org.drools.marshalling.impl.InputMarshaller.readFactHandles(InputMarshaller.java:373)
at org.drools.marshalling.impl.InputMarshaller.readSession(InputMarshaller.java:230)
at org.drools.marshalling.impl.DefaultMarshaller.unmarshall(DefaultMarshaller.java:92)
at org.drools.marshalling.impl.DefaultMarshaller.unmarshall(DefaultMarshaller.java:63)
at com.sample.DroolsTest.main(DroolsTest.java:50)

Provided is a testcase with two simple rules matching Fact objects directly and from the entry-point "facts".
A fact is inserted directly into the knowledgeSession and then it is marshalled and unmarshalled - which works fine.
Then a fact is inserted into a entry-point "facts" and the session is marshalled and unmarshalled - which throws the NPE.